The cochlea (A & B) is filled with fluid, and lined with tens of thousands of tiny hair cells (C & D). The following figures (A-E) show increasingly enlarged electron microscope images of the cochlea and hair cells. Figure A shows a sound wave’s journey to the cochlea.
The cochlea is responsible for changing the sound pressure waves (vibrations) into nerve inmpulses, which are then transferred to the auditory cortex (part of the temporal lobe) of the brain via the auditory nerve, for processing. Processing includes decoding the frequency distribution of the information contained in the neural impulses for meaning and spatial recognition (where is the sound located, and what does it mean).